The invention relates to a measuring method on an electric motor with a rotor and a stator for determining the fly height (lifted height) and/or axial play, the rotor being mounted, and in particular fluid-mounted, on the stator.
The invention also relates to a measuring device for an electric motor, by means of which an axial position of a rotor which is mounted, and in particular fluid-mounted, on a stator can be determined.
Fluid bearings or hydrodynamic bearings are used for example for the rotational mounting of spindle motors for hard disk drives. Such electric motors have high levels of running smoothness and accuracy along with great robustness and shock resistance. However, it is important when producing a fluid bearing that very close tolerances are maintained for the bearing gap between the shaft and the bearing mount. If, for example, the motor is operated at its nominal speed, then the rotor is in a specific relative axial position (lifted position or flying position) in relation to the stator. The associated fly height or lifted height along with the axial play characterizes the electric motor, and in particular is a measure of the quality of the electric motor.
Ball bearings also have axial play.